Conventionally, various methods have been applied to reduce reverberation echoes of an ultrasonic image (B-mode image) that interfere with a diagnosis. As one example of such a method, a method of compounding multiple pieces of B-mode images with various deflection angles in transmission and reception of ultrasonic waves by signal averaging has been known. Moreover, applying this method, a method has also been known in which a degree and a position of a reverberation echo component are estimated from B-mode images with various deflection angles, and a weight at signal averaging is adaptively controlled from an estimation result.
However, in the above method of compounding multiple images with various deflection angles, an influence of reduced amplitude when a deflection angle is increased cannot be avoided due to the constraint of element factors. That is, in an image taken in an inclined direction, the lateral resolution is degraded compared to an ordinary image with a deflection angle “0 degree” (center image). Furthermore, in an image taken in an inclined direction, the sensitivity (S/N ratio) relative to a center image is also degraded.
Therefore, in an output image that is obtained by compounding multiple images with various deflection angles, the lateral resolution and the sensitivity are degraded with respect to an ordinary center image.